Cellulose fiber and process for the production thereof

Abstract

The invention concerns a cellulose fiber of the genus Lyocell which is treated with a cross-linking agent, with the cross-linking agent inducing a protection from fibrillation on the fiber and exhibiting the following properties: the protection from fibrillation induced by the cross-linking agent changes if the fiber is stored within a pH range from 4.0 to 10.0, in particular under the influence of moisture and/or heat, within the pH range from 4.0 to 10.0, an optimum value exists at which the stability of the protection from fibrillation induced by the cross-linking agent during storage is highest a suitable range exists around the optimum value in which the stability is reduced by 20% at the most, compared to the stability at the optimum value, within the pH range from 4.0 to 10.0, the suitable range is limited by at least one limiting value at which the stability is reduced by 20% compared to the long-term stability at the optimum value and with a further decrease in stability occurring below and above said value, respectively, and the cross-linking agent has the capability to change the pH value. The fiber according to the invention is characterized in that the fiber comprises a buffering substance in the suitable range and exhibits a buffer capacity of at least about 12 mmol/kg fiber, preferably from about 15 to about 70 mmol/kg fiber, in the suitable range.

What is claimed is: 
     
       1. A cellulose fiber of the genus Lyocell which will be subjected to wet processing which is treated with a cross-linking agent, with the cross-linking agent inducing a protection from fibrillation on the fiber and exhibiting the following properties:
 the protection from fibrillation induced by the cross-linking agent changes if the fiber is stored within a pH range from about 4.0 to about 10.0; 
 within the pH range from about 4.0 to about 10.0, an optimum value exists at which the stability of the protection from fibrillation induced by the cross-linking agent during storage, before being subjected to said wet processing, is highest; 
 a suitable range exists around the optimum value in which the stability is reduced by 20% at the most, compared to the stability at the optimum value; 
 within the pH range from about 4.0 to about 10.0, the suitable range is limited by at least one limiting value at which the stability is reduced by 20% compared to the long-term stability at the optimum value and with a further decrease in stability occurring below and above said value, respectively; 
 the cross-linking agent has the capability to change the pH value, 
 wherein the fiber contains at least one buffering substance buffering in the suitable range and exhibits a buffer capacity of at least about 12 mmol/kg fiber in the suitable range; and 
 wherein the at least one buffering substance maintains the pH of the fiber in the suitable range during storage, before being subjected to said wet processing. 
 
     
     
       2. The cellulose fiber according to  claim 1 , wherein the at least one buffering substance has a pK a  value in the suitable range or outside of the suitable range by up to 1 pH unit. 
     
     
       3. The cellulose fiber according to  claim 1 , wherein the cross-linking agent is a substance of formula (I) 
       
         
           
           
               
               
           
         
       
       wherein X represents halogen, R═H or an ionic moiety and n=0 or 1, or a salt of said compound, respectively. 
     
     
       4. The cellulose fiber according to  claim 3 , wherein the fiber exhibits a pH value ranging from 8.5 to 10.5. 
     
     
       5. The cellulose fiber according to  claim 3  or  4 , wherein the at least one buffering substance has a pK a  value ranging from 8.0 to 11.0. 
     
     
       6. The cellulose fiber according to  claim 3  or  4 , wherein the buffering substance is selected from the group consisting of borax; carbonates or bicarbonates of alkali metal ions, ammonium or cations derived from substituted amines; phosphates, hydrogen phosphates or dihydrogen phosphates of alkali metal ions, ammonium or cations derived from substituted amines; ammonia; substituted amines; guanidine or guanidinium salts; and mixtures thereof as well as mixtures with carboxylic acids and salts thereof. 
     
     
       7. The cellulose fiber according to  claim 6 , wherein the buffering substance comprises borax in concentrations of at least 1525 mg borax per kg fiber. 
     
     
       8. The cellulose fiber according to  claim 7 , wherein the buffering substance comprises borax in concentrations from 2860 mg to 14000 mg borax per kg fiber. 
     
     
       9. The cellulose fiber according to  claim 6 , wherein the buffering substance comprises the buffer system sodium hydrogen carbonate/sodium carbonate in concentrations of at least 848 mg per kg fiber (calculated as sodium carbonate). 
     
     
       10. The cellulose fiber according to  claim 9 , wherein the buffering substance comprises the buffer system sodium hydrogen carbonate/sodium carbonate in concentrations from 1580 mg to 7420 mg per kg fiber (calculated as sodium carbonate). 
     
     
       11. The cellulose fiber according to  claim 1 , wherein the fiber exhibits a fiber moisture of 8-10%. 
     
     
       12. A bale of cellulose fibers, comprising cellulose fibers according to  claim 1 . 
     
     
       13. A yarn, woven fabrics, knitted fabrics, braided fabrics and hosieries, comprising cellulose fibers according to  claim 1 . 
     
     
       14. A process for the production of a cellulose fiber according to  claim 1 , comprising the step of applying a buffering substance in the suitable pH range onto a cellulose fiber of the genus Lyocell. 
     
     
       15. The process according to  claim 14 , wherein the application of the buffering substance occurs in the course of the manufacturing process for the cellulose fiber, before it is pressed into a bale. 
     
     
       16. The cellulose fiber according to  claim 1 , wherein the fiber contains a buffering substance in the suitable range and exhibits a buffer capacity of from about 15 to about 70 mmol/kg fiber in the suitable range. 
     
     
       17. The cellulose fiber according to  claim 3 , wherein the cross-linking agent is the sodium salt of 2,4-dichloro-6-hydroxy-1.3.5-triazine.